Farming Strategy Loop:

1. Farm Nightmare Dungeons (Tier 31+ recommended)
Focus on Diablo 4 Items speed-clears for Tribute drops.

2. Collect Tributes of Harmony
These drop more frequently in Escalating Nightmare tiers.

3. Enter Kurast Undercity
Apply the Tribute of Harmony before entering.

4. Speedrun the Undercity
Aim for high Attunement to maximize Rune rewards.

5. Collect Runes + Repeats
Rinse and repeat to scale the Rune inventory for Mythic crafting.

Rune Drop Rate Buff in Season 9

Another factor making this route exceptional is Season 9's buff to global Rune drop rates. Runes are more generous across the board, and when combined with the Tribute of Harmony's guaranteed drop, you're looking at one of the highest-yield farming routes in Diablo 4's history.

Alternate (But Less Reliable) Rune Farming Sources

While nothing beats the consistency of the Undercity method, some additional sources can help round out your Rune stockpile:

Lair Bosses

Bosses like Grigoire, Varshan, or Duriel can drop Runes (especially Legendary ones).
Great option when targeting Uber Unique or Summoning Mats anyway.

Helltide Chests

Good for general loot, with occasional Rune drops.
RNG-heavy but worth doing when Helltide is active.

Tree of Whispers Caches

Whisper Caches often contain Runes.
Useful for passive farming while clearing Bounties.

Augment Caches

Can be purchased with reputation in the Mercenary's Den.
Requires Tier 8 rapport with D4 materials for sale Aldkin, making it more late-game focused.